When attacking targets, firing commands, that is to say the launch angle and the instance of shot firing are chosen in order to achieve as high a hit probability as possible. The accuracy of weapon aiming, the munitions scatter and the atmospheric influences make this task harder. In order to counteract these disturbances, measures are taken, such as calibration during the aiming procedure or measurement of the air pressure and air temperature and wind. Furthermore, another factor is the variability of the muzzle velocity, which influences the time of flight of the projectile to the target. In practice, the muzzle velocity of the projectile is therefore often measured, and is taken into account in the fire control. For example, CH 691 143 A5 discloses an apparatus for measuring the projectile velocity at the muzzle of a weapon barrel. This comprises two sensors which are arranged at a distance from one another on a supporting tube, respond to a change in a magnetic flux, and are connected to evaluation electronics.
Additional error sources are, in particular, the unknown target movements between the time of firing the projectile and its arrival at the target. Particularly if the projectile has to fly over relatively long distances, it may be difficult to predetermine the predicted position of the target at the hit point. In order to reduce these errors, models of the target movement are formulated and are operated using target measurement data in order to identify the kinematics of the target. This data is then used, in general extrapolated, in the fire control in order to predict the target position after the expected time of flight.
However, with the exception of the radial velocity, the measurements are pure determined positions. The target velocity and, possibly, target acceleration are derived from these in the filter, and are used for the extrapolation. The accuracy of the extrapolated data is particularly dependent on the quality of the acceleration estimate. Furthermore, as soon as the target maneuvers and the accelerations become large for this reason, it is possible for the fire control to refuse the firing recommendation. The known residues of the filter, that is to say the difference between the estimate and the measurement, are therefore not very suitable for this purpose, because they include only the position error with respect to the target. In the event of a target maneuver, a certain amount of time always passes before the filter transforms the generated residues to acceleration. This is referred to as stabilization of the filter.
The total time delay between the target maneuver and the time of arrival of the projectile, whose fire elements take account of this maneuver, at the target is composed of:time delay=stabilization of the filter+time of flight of the projectile+other dead times.
In this case, other dead times means the time required for the measurement, for the data processing and for data transmission.
The fire control is improved by test projectiles or trial firings, and this can be referred to as a “closed loop”. In order to statistically improve the measurement results of the test projectiles, a limited number of them are fired successively. A firing burst whose first shots are measured at the target must in this case last longer than the projectile time of flight if its last shots are to profit from the corresponding corrections. Measurement systems such as these are complicated, and furthermore expensive, depending on the purpose.